RFID stands for Radio-Frequency IDentification. An RFID transponder, or ‘tag’, serves a similar purpose as a bar code or a magnetic strip on the back of a credit card; it provides an identifier for a particular object, although, unlike a barcode or magnetic strip, some tags support being written to. An RFID system carries data in these tags, and retrieves data from the tags wirelessly. Data within a tag may provide identification for an item in manufacture, goods in transit, a location, the identity of a vehicle, an animal, or an individual. By including additional data, the ability is provided for supporting applications through item-specific information or instructions available on reading the tag.
A basic RFID system includes a reader or ‘interrogator’ and a transponder (RF tag) electronically programmed with unique identifying information. Both the transceiver and transponder have antennas, which respectively emit and receive radio signals to activate the tag, read data from the tag, and write data to it. An antenna is a feature that is present in both readers and tags, and is essential for the communication between the two. An RFID system requires, in addition to tags, a mechanism for reading or interrogating the tags and usually requires some means of communicating RFID data to a host device, e.g., a computer or information management system. Often the antenna is packaged with the transceiver and decoder to become a reader (an ‘interrogator’), which can be configured either as a handheld or a fixed-mount device. The reader emits radio waves in ranges of anywhere from one inch to 100 feet or more, depending upon its power output and the radio frequency used. When an RFID tag passes through the electromagnetic zone (its ‘field’) created by the reader, it detects the reader's activation signal. The reader decodes the data encoded in the tag's integrated circuit and the data is often passed to a device (e.g., a computer) for processing.
Two methods distinguish and categorize RFID systems, one based upon close proximity electromagnetic or inductive coupling, and one based upon propagating electromagnetic waves. Coupling is via ‘antenna’ structures forming an integral feature in both tags and readers. While the term ‘antenna’ is generally considered more appropriate for propagating systems it is also loosely applied to inductive systems.
Transponders/Tags
The word transponder, derived from TRANSmitter/resPONDER, reveals the function of a tag. A tag responds to a transmitted or communicated request for the data it carries, the communication between the reader and the tag being wireless across the space between the two. The essential components that form an RFID system are one or more tags and a reader or interrogator. The basic components of a transponder are, generally speaking, fabricated as low power integrated circuit suitable for interfacing to an external coil, or utilizing ‘coil-on-chip’ technology, for data transfer and power generation, where the coil acts as an antenna matched to the frequency supported.
The Reader/Interrogator
Reader/interrogators can differ quite considerably in complexity, depending upon the type of tags being supported and the functions to be fulfilled. However, their overall function is to provide a mechanism for communicating with the tags, providing power to passive tags, and facilitating data transfer. Functions performed by the reader may include signal conditioning, parity error checking and correction. Once the signal from a transponder has been correctly received and decoded, algorithms may be applied to decide whether the signal is a repeat transmission, and may then instruct the transponder to cease transmitting. This is known as a ‘Command Response Protocol’ and is used to circumvent the problem of reading multiple tags in a short space of time. Using interrogators in this way is sometimes referred to as ‘Hands Down Polling’. An alternative, more secure, but slower tag polling technique is called ‘Hands Up Polling’, which involves the interrogator looking for tags with specific identities, and interrogating them in turn. This technique requires contention management, and a variety of techniques have been developed to improve the process of batch reading, including anti-collision techniques.
Current RFID systems require that a tag be in the field of the reader (interrogator), and powered on, in order for a user to interact with it. Furthermore, current tags are limited to the capabilities inherent in the tag. In multiple tag type environments, an RFID system is typically forced to use the common subset of tag capabilities, and has limited ability to support new or enhanced tags.
Previous embedded software systems have had limitations including the utilization of static software architectures whose specific software implementations are integral with their application-specific program or functionality. These monolithic implementations are often found in microcontroller-based designs wherein the embedded software or firmware has system resources and performance that are limited by the hardware.
Problem to be Solved
Traditional RFID applications have been closed loop and proprietary. Preexisting RFID readers are controlled by dedicated, closed-architecture, monolithic, embedded software (firmware). In previous RFID readers, features and functionality in the readers are set at compile time, and the readers are typically application specific. These readers do not allow a user or programmer to modify or upgrade only those specific aspects of a reader's functionality (i.e., code sections or modules) which the user/programmer would like to change. Rather, in order to modify segments of code in the reader with any reasonable degree of granularity, the entire reader firmware module must typically be re-programmed (e.g., ‘re-flashed’, in the typical case where the reader employs flash memory), or, in the case of multiple-processor readers, a relatively large part of the existing reader firmware must still be extensively re-programmed. Nor do preexisting RFID readers allow modularity or granularity with respect to the security level of specific modules (drivers/applications, etc.), so that, for example, the code in pre-selected proprietary modules may be kept secure (i.e., remain undecipherable to an unauthorized user/programmer), while the code in other specific modules may be readily re-programmed.
As markets such as contactless payment and supply chain management emerge, wide-scale adoption of RFID remains inhibited as the industry continues to deliver reader technology as monolithic hardwired devices with inaccessible RFID radio control software. Thus the benefits of RFID have been difficult to implement across a wider set of applications. For example, access control readers and animal scanners cannot be integrated into cell phones, DVD players or medical devices. Furthermore, because RFID readers have been delivered as vertically-integrated ‘black-box’ technology, software developers have not had access to the inner workings of the readers.
Even within retail supply chain, RFID reader requirements vary widely from stationary label printers to handheld devices and from forklifts to dock doors. Indeed there remains a problem in the industry that no standard technology can support the spectrum of reader requirements—from power and frequency control, to host interfaces, to tag protocols and standards, as well as the wide variety of price/performance tradeoffs related to read range and rate, physical size, power consumption and cost.